You mean, comic versions, or "actual"(fictional) versions? 'Cause, the comic versions, one is of Marvel, and one is of DC, so, they really can't be the same, unless someone did a badass crossover that revealed both to be the same, even though as cool as that would be, it would have to ignore a lot of canon and character integrity and blah blah blah blah blah...

In Marvel, Mephisto, Marduk Kurios (usually called Satan), Lucifer, Satannish, and many, many other Hell-Lords have claimed to be THE Satan at one time or another. To make things even more confusing, there is a theory that in the past, these big bads have temporarily merged their forms to create a "Satan" figure when they wish to do something of mutual importance.

In any case, it is next to impossible to determine who was which Satan in every appearance, unless it is actually said.